Bicomponent fibers including ethylene/alpha-olefin interpolymers

ABSTRACT

Provided are bicomponent fibers. The bicomponent fiber comprises a first region and a second region. The first region comprises a first ethylene/alpha-olefin interpolymer, and the second region comprises a second ethylene/alpha-olefin interpolymer. The first ethylene/alpha-olefin interpolymer has a highest peak melting temperature (Tm) less than 130° C. and at least 3.5° C. greater than a highest peak melting temperature of the second ethylene/alpha-olefin interpolymer. The bicomponent fibers can be used for forming nonwovens that in aspect have improved tensile strength, elongation at break, and/or abrasion resistance.

TECHNICAL FIELD

Embodiments of the present disclosure generally relate to bicomponent fibers that comprise ethylene/alpha-olefin interpolymers, and nonwovens comprising the fibers.

INTRODUCTION

Bicomponent fibers are fibers made up of two different regions and corresponding polymer compositions that are extruded from the same spinneret with both compositions contained within the same filament or fiber. When the fiber leaves the spinneret, it consists of non-mixed components that are fused at the interface. The two polymer compositions can differ in their chemical and/or physical properties. Bicomponent fibers can be formed by spinning techniques known in the art and can be used for forming a nonwoven. Nonwovens formed from bicomponent fibers can have similar or different properties than nonwovens formed from monocomponent fibers. Problems exist, however, with developing high spinnability, fine denier bicomponent fibers and nonwovens made from such bicomponent fibers that are recyclable and have a combination of excellent softness, tensile strength, abrasion resistance, and/or elongation at break.

SUMMARY

Embodiments of the present disclosure provide bicomponent fibers that are in aspects strong and highly spinnable as represented by high filament speed and low denier. The bicomponent fibers can be used to form nonwovens that are compatible with polyethylene recycling streams and can have a combination of enhanced tensile strength, abrasion resistance, and/or elongation at break. The bicomponent fibers includes a first region comprising a first ethylene/alpha-olefin interpolymer and a second region comprising a second ethylene/alpha-olefin interpolymer.

Disclosed herein is a bicomponent fiber. The bicomponent fiber comprises a first region and a second region; the first region comprising a first ethylene/alpha-olefin interpolymer having a highest peak melting temperature (Tm) of less than 130° C.; the second region comprising a second ethylene/alpha-olefin interpolymer having a density less than a density of the first ethylene/alpha-olefin interpolymer composition; wherein the highest peak melting temperature (Tm) of the first ethylene/alpha-olefin interpolymer is at least 3.5° C. greater than a highest peak melting temperature (Tm) of the second ethylene/alpha-olefin interpolymer; wherein the first region and second region are arranged in a core-sheath configuration.

Also disclosed herein is a nonwoven. The nonwoven is formed from the bicomponent fibers disclosed herein. In embodiments, the nonwoven has one or more of the following properties: a fiber denier equal to or less than 1.5 g/9000 m; a tensile strength in the machine direction greater than 11.0 Newton per one inch at 20 gram per square meter (gsm) of the nonwoven; an elongation at break in the machine direction greater than 100% at 20 gsm of the nonwoven; and an abrasion resistance in the machine direction of less than 0.18 mg/cm² at 20 gsm of the nonwoven. In embodiments, the nonwoven formed from the bicomponent fiber disclosed herein comprises at least 12 weight percent (wt.%) of the combined first ethylene/alpha-olefin interpolymer and second ethylene/alpha-olefin interpolymer at a temperature range of from 40.0° C. to 68.0° C. (WT_(40-68° C.)) on an elution profile via improved comonomer composition distribution (ICCD) procedure, where weight percent at a temperature range of from 40.0° C. to 68.0° C. on an elution profile via ICCD can be measured in accordance with the test method described below.

Additional features and advantages of the embodiments will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments described herein, including the detailed description which follows, the claims, as well as the appended drawing.

It is to be understood that both the foregoing and the following descriptions describe various embodiments and are intended to provide an overview or framework for understanding the nature and character of the claimed subject matter. The accompanying figures are included to provide a further understanding of the various embodiments, and are incorporated into and constitute a part of this specification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of a single reactor data flow diagram.

FIG. 2 is a schematic of a dual reactor data flow diagram.

FIG. 3 is an ICCD elution profile of nonwoven Inventive Example 2 displaying W_(T)(T) in relation to temperature at a temperature range of from 40.0° C. to 68.0° C. (WT_(40-68° C.)).

DETAILED DESCRIPTION

Aspects of the disclosed bicomponent fibers are described in more detail below. The bicomponent fibers can be used to form nonwovens, and such nonwovens can have a wide variety of applications, including, for example, wipes, face masks, tissues, bandages, medical gowns, baby diapers, adult incontinence, and other medical and hygiene products. It is noted however, that this is merely an illustrative implementation of the embodiments disclosed herein. The embodiments are applicable to other technologies that are susceptible to similar problems as those discussed above.

As used herein, the terms “comprising,” “including,” “having,” and their derivatives, are not intended to exclude the presence of any additional component, step or procedure, whether or not the same is specifically disclosed. In order to avoid any doubt, all compositions claimed through use of the term “comprising” may include any additional additive, adjuvant, or compound, whether polymeric or otherwise, unless stated to the contrary. In contrast, the term, “consisting essentially of” excludes from the scope of any succeeding recitation any other component, step or procedure, excepting those that are not essential to operability. The term “consisting of” excludes any component, step or procedure not specifically delineated or listed.

As used herein, the term “interpolymer” refers to polymers prepared by the polymerization of at least two different types of monomers. The term interpolymer thus includes copolymers (employed to refer to polymers prepared from two different types of monomers), and polymers prepared from more than two different types of monomers.

As used herein, the term “polymer” means a polymeric compound prepared by polymerizing monomers, whether of the same or a different type. The term polymer thus encompasses the term homopolymer (employed to refer to polymers prepared from only one type of monomer, with the understanding that trace amounts of impurities can be incorporated into the polymer structure), and the term interpolymer as defined above. A polymer may be a single polymer or polymer blend.

As used herein, the terms “nonwoven,” “nonwoven web,” and “nonwoven fabric” are used herein interchangeably. “Nonwoven” refers to a web or fabric having a structure of individual fibers or threads which are randomly interlaid, but not in an identifiable manner as is the case for a knitted fabric.

As used herein, the term “spunbond” refers to the fabrication of nonwoven fabric including the following steps: (a) extruding molten thermoplastic strands from a plurality of fine capillaries called a spinneret; (b) quenching the strands with a flow of air which is generally cooled in order to hasten the solidification of the molten strands; (c) attenuating the strands by advancing them through the quench zone with a draw tension that can be applied by either pneumatically entraining the strands in an air stream or by winding them around mechanical draw rolls of the type commonly used in the textile fibers industry; (d) collecting the drawn strands into a web on a foraminous surface (e.g., moving screen or porous belt); and (e) bonding the web of loose strands into a nonwoven fabric. Bonding can be achieved by a variety of means including, but not limited to, thermo-calendaring process, adhesive bonding process, hot air bonding process, needle punch process, hydroentangling process, and combinations thereof.

As used herein, the term “meltblown” refers to the fabrication of nonwoven fabrics via a process which generally includes the following steps: (a) extruding molten thermoplastic strands from a spinneret; (b) simultaneously quenching and attenuating the polymer stream immediately below the spinneret using streams of high velocity heated air; (c) collecting the drawn strands into a web on a collecting surface. Meltblown webs can be bonded by a variety of means including, but not limited to, autogeneous bonding, i.e., self bonding without further treatment, thermo-calendaring process, adhesive bonding process, hot air bonding process, needle punch process, hydroentangling process, and combinations thereof.

A bicomponent fiber may comprise a combination of two or more suitable embodiments as disclosed herein.

A nonwoven formed from a bicomponent fiber may comprises a combination of two or more suitable embodiments as disclosed herein.

Fibers

The bicomponent fiber according to embodiments of the present disclosure can be formed into a fiber via different techniques, for example, via melt spinning In melt spinning, the first region and second region can be melted. coextruded, and forced through fine orifices in a metallic plate, spinneret, into air or other gas, where the coextruded regions are cooled and solidified for forming bicomponent fibers. The solidified filaments can be drawn off via air jets, rotating rolls, or godets, and can be laid on a conveyer belt as a web for forming a nonwoven. The bicomponent fiber according to embodiments of the present disclosure contains two regions (i.e., a first region and a second region). The regions can be configured in a core-sheath configuration, namely referring herein to a concentric core-sheath or islands-in-the-sea configuration. For example, in embodiments, the first region and second region are arranged in a concentric core-sheath configuration, where the first region is a core region and the second region is a sheath region and the sheath region surrounds the core region. In other embodiments, the first region and the second region are arranged in an core-sheath, islands-in-the-sea configuration, where the first region is multiple core regions (also referred to as islands) and the second region is a sheath region (also referred to as a sea), and the sheath region or sea surrounds the multiple core regions or islands.

In embodiments, the bicomponent fiber comprises a first region and a second region, wherein the weight ratio of the first region to the second region is 10:90 to 90:10. All individual values and subranges of a ratio of from 90:10 to 10:90 are disclosed and included herein. For example, in embodiments, the weight ratio of the first region to the second region can be from 80:20 to 20:80, from 70:30 to 30:70, from 60:40 to 40:60, or from 55:45 to 45:55.

In embodiments, the bicomponent fiber has a denier of less than 50 g/9000 m. All individual values and subranges of less than 50 g/9000 m are disclosed and included herein. For example, the bicomponent fiber can have a denier of less than 40, less than 30, less than 20, less than 10, less than 5, less than 3, less than 2, less than 1.5, or less than 1.2 g/9000m, or can have a denier in the range of from 0.1 to 50, 0.1 to 40, 0.1 to 30, 0.1 to 20, 0.1 to 10, 0.1 to 5, 0.1 to 2.0, 0.1 to 1.5, 0.1 to 1.2, 1 to 50, 1 to 40. 1 to 30, Ito 20, 1 to 10, 1 to 5, 1 to 2.0, 1 to 1.5, or 1 to 1.2 g/9000 m. where denier can be measured in accordance with the test method described below.

First Region

The first region of the bicomponent fiber comprises a first ethylene/alpha-olefin interpolymer.

In embodiments, the first region of the bicomponent fiber comprises a first ethylene/alpha-olefin interpolymer in an amount of at least 50 weight percent (wt. %) based on total weight of the first region. All individual values and subranges of at least 50 wt. % are disclosed and included herein. For example, in embodiments, the first region can comprise a first ethylene/alpha-olefin interpolymer in an amount of at least 50 wt. %, at least 60 wt. %, at least 75 wt. %, at least 85 wt. %, at least 90 wt. %, at least 95 wt. %, or at least 99 wt. %, based on the total weight of the first region. In other embodiments, the first region can comprises a first ethylene/alpha-olefin interpolymer in an amount of from 50 to 100 wt. %, 60 to 100 wt. %, 75 to 100 wt. %, 85 to 100 wt. %, 90 to 100 wt. %, 95 to 100 wt. %, 99 to 100 wt. %, 50 to 95 wt. %, 60 to 95 wt. %, 75 to 95 wt. %, 85 to 95 wt. %, or 90 to 95 wt. %, based on the total weight of the first region.

The term “ethylene/alpha-olefin interpolymer” refers to polymers comprising ethylene and an alpha-olefin having 3 or more carbon atoms. In embodiments, the first ethylene/alpha-olefin interpolymer comprises greater than 55 wt. % of the units derived from ethylene and less than 45 wt. % of the units derived from one or more alpha-olefin comonomers (based on the total amount of polymerizable monomers). All individual values and subranges of greater than 55 wt. % of the units derived from ethylene and less than 45 wt. % of the units derived from one or more alpha-olefin comonomers are included and disclosed herein. For example, in embodiments, the first ethylene/alpha-olefin interpolymer can comprise (a) greater than 55%, greater than 70%, greater than 85%, greater than 90%, greater than 92%, greater than 95%, greater than 97%, greater than 98%, greater than 99%, greater than 99.5%, or from 55% to 99.5%, from 55% to 95% from 55% to 90%, from 55% to 99.5%, from 55% to 99%, from 55% to 97%, from 55% to 94%, from 75% to 90%, from 90% to 99.9%, from 90% to 99.5% from 90% to 97%, or from 90% to 95% by weight, of the units derived from ethylene; and (b) less than 45%, less than 30%, less than 20%, less than 18%, less than 15%, less than 12%, less than 10%, less than 8%, less than 5%, less than 4%, less than 3%, less than 2%. less than 1%, or from 0.1 to 45%, from 0.1 to 25%, from 0.1 to 10%, from 0.1 to 5%, from 0.5 to 20%, from 0.5 to 10%, from 0.5 to 5%, from 1 to 20%, from 1 to 10%, from 1 to 5%, from 5 to 20%, or from 5 to 10%, by weight, of units derived from one or more a-olefin comonomers. The comonomer content may be measured using any suitable technique, such as techniques based on nuclear magnetic resonance (“NMR”) spectroscopy, and, for example, by ¹³C NMR analysis as described in U.S. Pat. No. 7,498,282, which is incorporated herein by reference.

Suitable alpha-olefin comonomers typically have no more than 20 carbon atoms. The one or more alpha-olefins of the first ethylene/alpha-olefin interpolymer may be selected from the group consisting of C3-C20 acetylenic ally unsaturated monomers and C4-C18 diolefins. For example, the alpha-olefin comonomers may have 3 to 10 carbon atoms, or 3 to 8 carbon atoms. Exemplary alpha-olefin comonomers include, but are not limited to, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, and 4-methyl-1-pentene. The one or more alpha-olefin comonomers of the first ethylene/alpha-olefin interpolymer may, for example, be selected from the group consisting of propylene, 1-butene, 1-hexene, and 1-octene; or in the alternative, from the group consisting of 1-butene, 1-hexene and 1-octene, or in the alternative, from the group consisting of 1-hexene and 1-octene. In one or more embodiments, the first ethylene/alpha-olefin interpolymer may comprise greater than 0 wt. % and less than 45 wt. % of units derived from one or more of 1-octene, 1-hexene, or 1-butene comonomers.

In embodiments, the first ethylene/alpha-olefin interpolymer has a density in the range of from 0.940 to 0.965 g/cm³. All individual values and subranges of a density in the range of from 0.940 to 0.965 g/cm³ are disclosed and included herein. For example, the first ethylene/alpha-olefin interpolymer can have a density in the range of from 0.940 to 0.965 g/cm³, 0.940 to 0.960 g/cm³, 0.945 to 0.965 g/cm³, 0.945 to 0.960 g/cm³, 0.950 to 0.965 g/cm³, or 0.950 to 0.960 g/cm³, where density can be measured according to ASTM D792.

In embodiments, the first ethylene/alpha-olefin interpolymer has a melt index (I2), measured according to ASTM D1238, 190° C., 2.16 kg, in the range of from 10 to 60 g/10 minutes. All individual values and subranges of from 10 to 60 g/10 minutes are included and disclosed herein. For example, in some embodiments, the first ethylene/alpha-olefin interpolymer can have a melt index (12) in the range of from 10 to 60 g/10 minutes, from 10 to 50 g/10 minutes, from 10 to 40 g/10 minutes, from 10 to 30 g/10 minutes, from 10 to 20 g/10 minutes, from 20 to 60 g/10 minutes, from 20 to 50 g/10 minutes, from 20 to 40 g/10 minutes, from 20 to 30 g/10 minutes, from 15 to 60 g/10 minutes, from 15 to 50 g/10 minutes, from 15 to 40 g/10 minutes, from 15 to 30 g/10 minutes, or from 15 to 20 g/10 minutes, where melt index (I2) can be measured according to ASTM D1238, 190° C., 2.16 kg.

In embodiments, the first ethylene/alpha-olefin interpolymer has a molecular weight distribution, determined by conventional gel permeation chromatography (GPC) and expressed as the ratio of the weight average molecular weight to number average molecular weight (M_(w(GPC))/M_(n(GPC))), of from 1.5 to 5.0. All individual values and subranges of a molecular weight distribution (M_(w(GPC))/M_(n(GPC))) of from 1.5 to 5.0 are disclosed and included herein. For example, the first ethylene/alpha-olefin interpolymer can have a molecular weight distribution (M_(w(GPC))/M_(n(GPC))) of from 1.5 to 5.0, 1.5 to 4.0, 1.5 to 3.0, 1.5 to 2.5, 2.0 to 5.0, 2.0 to 4.0, 2.0 to 3.0, or 2.0 to 2.5, where molecular weight distribution (M_(w(GPC))/M_(n(GPC))) can be measured in accordance with the conventional GPC test method described below.

In embodiments, the first region can comprise further components, such as, one or more other polymers and/or one or more additives. Other polymers can include another ethylene/alpha-olefin interpolymer, a post-consumer or post-industrial recycled polymer, a polyester, a propylene-based polymer (e.g. polypropylene homopolymer, propylene-ethylene copolymer, or propylene/alpha-olefin interpolymer), or a propylene-based plastomer or elastomer. The amount of the other polymer may be up to 50 wt. % based on the total weight of the first region. For example, in embodiments, the first region can comprise up to 50 wt. % of a propylene-based plastomer or propylene-based elastomer (such as VERSIFY™ polymers available from The Dow Chemical Company and VISTAMAXX™ polymers available from ExxonMobil Chemical Co.), low modulus and/or low molecular weight polypropylene (such as L-MODU™ polymer from Idemitsu), random copolypropylene, or a propylene-based olefin block copolymer (such as INTUNE™). Potential additives include, but are not limited to, antistatic agents, color enhancers, dyes, lubricants, fillers, pigments, primary antioxidants, secondary antioxidants, processing aids, UV stabilizers, anti-blocks, slip agents, tackifiers, fire retardants, anti-microbial agents, odor reducer agents, anti-fungal agents, and combinations thereof. The first region can comprise from about 0.01 or 0.1 or 1 to about 25 or about 20 or about 15 or about 10 or about 5 weight percent by the combined weight of additives, based on the total weight of the first region.

In embodiments, the first ethylene/alpha-olefin interpolymer has a highest peak melting temperature (Tm) of less than 130° C., when measured according to the Differential Scanning Calorimetry (DSC) test method described below. All individual values and subranges of less than 130° C. are disclosed and incorporated herein. For example, in embodiments, the highest peak melting temperature (Tm) of the first ethylene/alpha-olefin interpolymer can be less than 130° C., less than 129.5° C., less than 129° C., or less than 128.5° C., or can be in the range of from 120° C. to 130° C., 125° C. to 130° C., 127° C. to 130° C., 128° C. to 130° C., 125° C. to 129.5° C., 126° C. to 129° C., 126° C. to 128° C., 127° C. to 129° C., 127° C. to 128.5° C., or 127° C. to 128° C., when measured according to the DSC test method described below.

In embodiments, the first ethylene/alpha-olefin interpolymer has a highest peak crystallization temperature (Tc) in the range of from 108° C. to 118° C., where highest peak crystallization temperature (Tc) can be measured according to the DSC test method described below. All individual values and subranges of from 108° C. to 118° C. are disclosed and included herein. For example, the first ethylene/alpha-olefin interpolymer can have a highest peak crystallization temperature (Tc) in the range of from 108° C. to 118° C., 110° C. to 118° C., 112° C. to 118° C., 108° C. to 116° C., 108° C. to 115° C., 110° C. to 116° C., 110° C. to 115° C., 112° C. to 116° C., or 113° C. to 115° C., when measured according to the DSC test method described below.

Second Region

The second region of the bicomponent fiber comprises a second ethylene/alpha-olefin interpolymer.

In embodiments, the second region of the bicomponent fiber comprises a second ethylene/alpha-olefin interpolymer in an amount of at least 50 weight percent (wt. %) based on total weight of the second region. All individual values and subranges of at least 50 wt. % are disclosed and included herein. For example, in embodiments, the second region can comprise a second ethylene/alpha-olefin interpolymer in an amount of at least 50 wt. %, at least 60 wt. %, at least 75 wt. %, at least 85 wt. %, at least 90 wt. %, at least 95 wt. %, or at least 99 wt. %, based on the total weight of the second region. In other embodiments, the second region can comprises a second ethylene/alpha-olefin interpolymer in an amount of from 50 to 100 wt. %, 60 to 100 wt. %, 75 to 100 wt. %, 85 to 100 wt. %, 90 to 100 wt. %, 95 to 100 wt. %, 99 to 100 wt. %, 50 to 95 wt. %, 60 to 95 wt. %, 75 to 95 wt. %, 85 to 95 wt. %, or 90 to 95 wt. %, based on the total weight of the second region.

In embodiments, the second ethylene/alpha-olefin interpolymer comprises greater than 55 wt. % of the units derived from ethylene and less than 45 wt. % of the units derived from one or more alpha-olefin comonomers (based on the total amount of polymerizable monomers). All individual values and subranges of greater than 55 wt. % of the units derived from ethylene and less than 45 wt. % of the units derived from one or more alpha-olefin comonomers are included and disclosed herein. For example, the second ethylene/alpha-olefin interpolymer can comprise (a) greater than 55%, greater than 70%, greater than 85%, greater than 90%, greater than 92%, greater than 95%, greater than 97%, greater than 98%, greater than 99%, greater than 99.5%, or from 55% to 99.5%, from 55% to 95% from 55% to 90%, from 55% to 99.5%, from 55% to 99%, from 55% to 97%, from 55% to 94%, from 75% to 90%, from 90% to 99.9%, from 90% to 99.5% from 90% to 97%, or from 90% to 95% by weight, of the units derived from ethylene; and (b) less than 45%, less than 30%, less than 20%, less than 18%, less than 15%, less than 12%, less than 10%, less than 8%, less than 5%, less than 4%, less than 3%, less than 2%, less than 1%, or from 0.1 to 45%, from 0.1 to 25%, from 0.1 to 10%, from 0.1 to 5%, from 0.5 to 20%, from 0.5 to 10%, from 0.5 to 5%, from 1 to 20%, from 1 to 10%, from 1 to 5%, from 5 to 20%, or from 5 to 10%, by weight, of units derived from one or more α-olefin comonomers. The comonomer content may be measured using any suitable technique, such as techniques based on nuclear magnetic resonance (“NMR”) spectroscopy, and, for example, by ¹³C NMR analysis as described in U.S. Pat. No. 7,498,282, which is incorporated herein by reference.

Suitable alpha-olefin comonomers typically have no more than 20 carbon atoms. The one or more alpha-olefins of the second ethylene/alpha-olefin interpolymer may be selected from the group consisting of C3-C20 acetylenically unsaturated monomers and C4-C18 diolefins. For example, the alpha-olefin comonomers may have 3 to 10 carbon atoms, or 3 to 8 carbon atoms. Exemplary alpha-olefin comonomers include, but are not limited to, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, and 4-methyl-1-pentene. The one or more alpha-olefin comonomers of the second ethylene/alpha-olefin interpolymer may, for example, be selected from the group consisting of propylene, 1-butene, 1-hexene, and 1-octene; or in the alternative, from the group consisting of 1-butene, 1-hexene and 1-octene, or in the alternative, from the group consisting of 1-hexene and 1-octene. In one or more embodiments, the second ethylene/alpha-olefin interpolymer may comprise greater than 0 wt. % and less than 45 wt. % of units derived from one or more of 1-octene, 1-hexene, or 1-butene comonomers.

In embodiments, the second ethylene/alpha-olefin interpolymer has a density that is less than the density of the first ethylene/alpha-olefin interpolymer. In embodiments, the density of the first ethylene/alpha-olefin interpolymer is at least 0.022 g/cm³ greater than the density of the second ethylene/alpha-olefin interpolymer. All individual values and subranges of at least 0.022 g/cm³ are included and disclosed herein; for example, the density of the first ethylene/alpha-olefin interpolymer can be at least 0.022 g/cm³, 0.025 g/cm³, 0.027 g/cm³, 0.029 g/cm³, 0.031 g/cm³, 0.033 g/cm³, 0.035 g/cm³, 0.037 g/cm³, 0.039 g/cm³, or 0.041 g/cm³ greater than the density of the second ethylene/alpha-olefin interpolymer, where density can be measured in accordance with ASTM D792. In other embodiments, the difference of the density of the first ethylene/alpha-olefin interpolymer and the density of the second ethylene/alpha-olefin interpolymer is in the range of from 0.023 to 0.085 g/cm³, 0.023 to 0.050 g/cm³, 0.023 to 0.040 g/cm³, 0.029 to 0.085 g/cm³, 0.029 to 0.050 g/cm³, 0.031 to 0.085 g/cm³, 0.031 to 0.050 g/cm³, 0.031 to 0.040 g/cm³, 0.039 to 0.050 g/cm³, or 0.039 to 0.085 g/cm³, where density can be measured in accordance with ASTM D792.

In embodiments, the second ethylene/alpha-olefin interpolymer has a density in the range of from 0.880 to 0.940 g/cm³. All individual values and subranges of a density in the range of from 0.880 to 0.940 g/cm³ are disclosed and included herein. For example, in some embodiments, the second ethylene/alpha-olefin interpolymer can have a density in the range of from 0.880 to 0.940 g/cm³, 0.880 to 0.930 g/cm³, 0.880 to 0.920 g/cm³, 0.890 to 0.940 g/cm³, 0.890 to 0.930 g/cm³, 0.890 to 0.920 g/cm³, 0.890 to 0.910 g/cm³, 0.900 to 0.940 g/cm³, 0.900 to 0.930 g/cm³, 0.900 to 0.920 g/cm³, or 0.900 to 0.910 g/cm³, where density can be measured according to ASTM D792.

In embodiments, the second ethylene/alpha-olefin interpolymer has a melt index (I2), measured according to ASTM D1238, 190° C., 2.16 kg, in the range of from 10 to 60 g/10 minutes. All individual values and subranges of from 10 to 60 g/10 minutes are included and disclosed herein. For example, in some embodiments, the second ethylene/alpha-olefin interpolymer can have a melt index (I2) in the range of from 10 to 60 g/10 minutes, from 10 to 50 g/10 minutes, from 10 to 40 g/10 minutes, from 10 to 30 g/10 minutes, from 10 to 20 g/10 minutes, from 20 to 60 g/10 minutes, from 20 to 50 g/10 minutes, from 20 to 40 g/10 minutes, from 20 to 30 g/10 minutes, from 15 to 60 g/10 minutes, from 15 to 50 g/10 minutes, from 15 to 40 g/10 minutes, from 15 to 30 g/10 minutes, or from 15 to 20 g/10 minutes, where melt index (I2) can be measured according to ASTM D1238, 190° C., 2.16 kg.

In embodiments, the second ethylene/alpha-olefin interpolymer has a molecular weight distribution, expressed as the ratio of the weight average molecular weight to number average molecular weight (M_(w(GPC))/M_(n(GPC))), of from 1.5 to 5.0. All individual values and subranges of a molecular weight distribution (M_(w(GPC))/M_(n(GPC))) of from 1.5 to 5.0 are disclosed and included herein. For example, the second ethylene/alpha-olefin interpolymer can have a molecular weight distribution (M_(w(GPC))/M_(n(GPC))) of from 1.5 to 5.0, 1.5 to 4.0, 1.5 to 3.0, 1.5 to 2.5, 2.0 to 5.0, 2.0 to 4.0, 2.0 to 3.0, or 2.0 to 2.5, where molecular weight distribution (M_(w(GPC))/M_(n(GPC))) can be measured in accordance with the conventional Gel Permeation Chromatography (GPC) test method described below.

In embodiments, the second region can comprise further components, such as, one or more other polymers and/or one or more additives. Other polymers can include another ethylene/alpha-olefin interpolymer, a polyester, post-consumer or post-industrial recycled polymer, a propylene-based polymer (e.g. polypropylene homopolymer, propylene-ethylene copolymer, or propylene/alpha-olefin interpolymer), or a propylene-based plastomer or elastomer. The amount of the other polymer may be up to 50 wt. % based on the total weight of the second region. For example, in embodiments, the second region can comprise up to 50 wt. % of a propylene-based plastomer or propylene-based elastomer (such as VERSIFY™ polymers available from The Dow Chemical Company and VISTAMAXX™ polymers available from ExxonMobil Chemical Co.), low modulus or/and low molecular weight polypropylene (such as L-MODU™ polymer from Idemitsu), random copolypropylene, or a propylene-based olefin block copolymer (such as INTUNE™). Potential additives include, but are not limited to, antistatic agents, color enhancers, dyes, lubricants, fillers, pigments, primary antioxidants, secondary antioxidants, processing aids, UV stabilizers, anti-blocks, slip agents, tackifiers, fire retardants, anti-microbial agents, odor reducer agents, anti-fungal agents, and combinations thereof. The second region can contain from about 0.01 or 0.1 or 1 to about 25 or about 20 or about 15 or about 10 or about 5 weight percent by the combined weight of additives, based on the total weight of the second region.

In embodiments, the first ethylene/alpha-olefin interpolymer has a highest peak melting temperature (Tm) of less than 130° C., and the highest peak melting temperature (Tm) of the first ethylene/alpha-olefin interpolymer is at least 3.5° C. greater than a highest peak melting temperature (Tm) of the second ethylene/alpha-olefin interpolymer, where highest peak melting temperature (Tm) can be measured in accordance with the DSC test method described below. All individual values and subranges of at least 3.5° C. are disclosed and included herein. For example, in some embodiments, the highest peak melting temperature (Tm) of the first ethylene/alpha-olefin interpolymer is at least 3.5° C. greater than, at least 4.0° C. greater than, at least 4.5° C. greater than, or at least 5° C. greater than a highest peak melting temperature (Tm) of the second ethylene/alpha-olefin interpolymer. In other embodiments, the difference between the highest peak melting temperature (Tm) of the first ethylene/alpha-olefin interpolymer and a highest peak melting temperature (Tm) of the second ethylene/alpha-olefin interpolymer is in the range of from 3.5° C. to 60° C., 4.0° C. to 60° C., 4.5° C. to 60° C., 5° C. to 60° C., 3.5° C. to 45° C., 4.0° C. to 45° C., 5° C. to 45° C., 3.5° C. to 30° C., 4.0° C. to 30° C., 4.5° C. to 30° C., 5° C. to 30° C., 3.5° C. to 15° C., 4.0° C. to 15° C., 4.5° C. to 15° C., or 5° C. to 15° C., where highest peak melting temperature (Tm) can be measured in accordance with the DSC test method described below.

In embodiments, the second ethylene/alpha-olefin interpolymer has a highest peak melting temperature (Tm) of less than 127.5° C., when measured according to the DSC test method describe below. All individual values and subranges of less than 127.5° C. are disclosed and incorporated herein. For example, in embodiments, the highest peak melting temperature (Tm) of the second ethylene/alpha-olefin interpolymer can be less than 127° C., less than 126.5° C., less than 126° C., less than 125.5° C., less than 125° C., less than 124.5° C., less than 124° C., less than 123.5° C., or less than 123° C., or can be in the range of from 90° C. to 127.5° C., 100° C. to 127.5° C., 110° C. to 127.5° C., 120° C. to 127.5° C., 122° C. to 127.5° C., 90° C. to 126° C., 100° C. to 126° C., 110° C. to 126° C., 120° C. to 126° C. 122° C. to 126° C., 90° C. to 124° C., 100° C. to 124° C., 110° C. to 124° C., 120° C. to 124° C., or 122° C. to 124° C., where highest peak melting temperature (Tm) can be measured in accordance with the DSC test method described below.

In embodiments, the second ethylene/alpha-olefin interpolymer has a highest peak crystallization temperature (Tc) in the range of from 90° C. to 114.5° C., where highest peak crystallization temperature (Tc) can be measured according to the DSC test method described below. All individual values and subranges of from 90° C. to 114.5° C. are disclosed and included herein. For example, the second ethylene/alpha-olefin interpolymer can have a highest peak crystallization temperature (Tc) in the range of from 90° C. to 114.5° C., 90° C. to 110° C., 90° C. to 105° C., 95° C. to 100° C., 95° C. to 110° C., 95° C. to 105° C., or 95° C. to 100° C., 90° C. to 114° C., 90° C. to 113° C., or 90° C. to 112° C., where highest peak crystallization temperature (Tc) can be measured according to the DSC test method described below.

In embodiments, the first ethylene/alpha-olefin interpolymer has a highest peak crystallization temperature (Tc) at least 3.5° C. greater than a highest peak crystallization temperature (Tc) of the second ethylene/alpha-olefin interpolymer. All individual values and subranges of at least 3.5° C. greater than are included and disclosed herein. For example, the first ethylene/alpha-olefin interpolymer can have a highest peak crystallization temperature (Tc) at least 3.5° C. greater than, at least 5° C. greater than, at least 7.5° C. greater than, at least 10° C. greater than, at least 11° C. greater than, at least 15° C. greater than, or at least 17° C. greater than, a highest peak crystallization temperature (Tc) of the second ethylene/alpha-olefin interpolymer, where highest peak crystallization temperature (Tc) can be measured according to the DSC test method described below. In other embodiments, the difference between a highest peak crystallization temperature (Tc) of the first ethylene/alpha-olefin interpolymer and a highest peak crystallization temperature (Tc) of the second ethylene/alpha-olefin interpolymer is in the range of from 3.5° C. to 25° C., 5° C. to 25° C., 10° C. to 25° C., 15° C. to 25° C., 3.5° C. to 20° C., 5° C. to 20° C., 10° C. to 20° C., 15° C. to 20° C., 3.5° C. to 15° C., 5° C. to 15° C., or 10° C. to 15° C., where highest peak crystallization temperature (Tc) can be measured according to the DSC test method described below.

Synthesis of First or Second Ethylene/Alpha-Olefin Interpolymers

Any conventional polymerization processes can be employed to produce the first or second ethylene/alpha-olefin interpolymer. Such conventional polymerization processes include, but are not limited to, solution polymerization process, using one or more conventional reactors (e.g. loop reactors, isothermal reactors, stirred tank reactors, batch reactors in parallel, series, and/or any combinations thereof). Such conventional polymerization processes also include gas-phase, solution or slurry polymerization or any combination thereof, using any type of reactor or reactor configuration known in the art.

In embodiments, the solution phase polymerization process occurs in one or more well-stirred reactors such as one or more loop reactors at a temperature in the range of from 115 to 250° C.; for example, from 155 to 225° C., and at pressures in the range of from 300 to 1000 psi; for example, from 400 to 750 psi. In one embodiment in a dual reactor, the temperature in the first reactor temperature is in the range of from 115 to 190° C., for example, from 115 to 170° C., and the second reactor temperature is in the range of 150 to 210° C., for example, from 170 to 205° C. In another embodiment in a single reactor, the temperature in the reactor temperature is in the range of from 115 to 250° C., for example, from 155 to 225° C. The residence time in a solution phase polymerization process is typically in the range of from 2 to 30 minutes; for example, from 5 to 20 minutes. Ethylene, solvent, one or more catalyst systems, optionally one or more cocatalysts, optionally one or more impurity scavengers, and optionally one or more comonomers are fed continuously to one or more reactors. Exemplary solvents include, but are not limited to, isoparaffins. For example, such solvents are commercially available under the name ISOPAR E from ExxonMobil Chemical Co., Houston, Tex. The resultant mixture of the first or second polyethylene composition and solvent is then removed from the reactor and the first or second polyethylene composition is isolated. Solvent is typically recovered via a solvent recovery unit, i.e. heat exchangers and vapor liquid separator drum, and is then recycled back into the polymerization system.

In one embodiment, the first or second ethylene/alpha-olefin interpolymer may be produced via a solution polymerization process in a dual reactor system, for example a dual loop reactor system, wherein ethylene and optionally one or more a-olefins are polymerized in the presence of one or more catalyst systems. Additionally, one or more co-catalysts may be present. In another embodiment, the first or second ethylene/alpha-olefin interpolymer may be produced via a solution polymerization process in a single reactor system, for example a single loop reactor system, wherein ethylene and optionally one or more a-olefins are polymerized in the presence of one or more catalyst systems.

An example of a catalyst system suitable for producing the first ethylene/alpha-olefin interpolymer can be a catalyst system comprising a procatalyst component comprising a metal-ligand complex of formula (I):

In formula (I), M is a metal chosen from titanium, zirconium, or hafnium, the metal being in a formal oxidation state of +2, +3, or +4; n is 0, 1, or 2; when n is 1, X is a monodentate ligand or a bidentate ligand; when n is 2, each X is a monodentate ligand and is the same or different; the metal-ligand complex is overall charge-neutral; each Z is independently chosen from —O—, —S—, —N(R^(N))-, or —P(R^(P))-, wherein independently each R^(N) and R^(P) is (C1-C30)hydrocarbyl or (C1-C30)heterohydrocarbyl; L is (C₁-C₄₀)hydrocarbylene or (C₁-C₄₀)heterohydrocarbylene, wherein the (C₁-C₄₀)hydrocarbylene has a portion that comprises a 1-carbon atom to 10-carbon atom linker backbone linking the two Z groups in Formula (I) (to which L is bonded) or the (C₁-C₄₀)heterohydrocarbylene has a portion that comprises a 1-atom to 10-atom linker backbone linking the two Z groups in Formula (I), wherein each of the 1 to 10 atoms of the 1-atom to 10-atom linker backbone of the (C₁-C₄₀)heterohydrocarbylene independently is a carbon atom or heteroatom, wherein each heteroatom independently is O, S, S(O), S(O)₂, Si(R^(C))₂, Ge(R^(C))₂, P(R^(C)), or N(R^(C)), wherein independently each R^(C) is (C₁-C₃₀)hydrocarbyl or (C₁-C₃₀)heterohydrocarbyl; R¹ and R⁸ are independently selected from the group consisting of —H, (C₁-C₄₀)hydrocarbyl, (C₁-C₄₀)heterohydrocarbyl, —Si(R^(C))₃, —Ge(R^(C))₃, —P(R^(P))₂, —N(R^(N))₂, —OR^(C), —SR^(C), —NO₂, —CN, —CF₃, R^(C)S(O)—, R^(C)S(O)²—, (R^(C))₂C═N—, R^(C)C(O)O—, R^(C)OC(O)—, R^(C)C(O)N(R^(N))—, (R^(N))₂NC(O)—, halogen, and radicals having formula (II), formula (III), or formula (IV):

In formulas (II), (III), and (IV), each of R³¹⁻³⁵, R⁴¹⁻⁴⁸, or R⁵¹⁻⁵⁹ is independently chosen from (C₁-C₄₀)hydrocarbyl, (C₁-C₄₀)heterohydrocarbyl, —Si(R^(C))₃, —Ge(R^(C))₃, —P(R^(P))₂, —N(R^(N))₂, —N═CHR^(C), —OR^(C), —SR^(C), —NO₂, —CN, —CF₃, R^(C)S(O)—, R^(C)S(O)₂—, (R^(C))₂C═N—, R^(C)C(O)O—, R^(C)OC(O)—, R^(C)C(O)N(R^(N))—, (R^(N))₂NC(O)—, halogen, or —H, provided at least one of R¹ or R⁸ is a radical having formula (II), formula (III), or formula (IV) where R^(C), R^(N), and R^(P) are as defined above.

In formula (I), each of R²⁻⁴, R⁵⁻⁷, and R⁹⁻¹⁶ is independently selected from (C₁-C₄₀)hydrocarbyl, (C₁-C₄₀)heterohydrocarbyl, —Si(R^(C))₃, —Ge(R^(C))₃, —P(R^(P))₂, —N(R^(N))₂, —N═CHR^(C), —OR^(C), —SR^(C), —NO₂, —CN, —CF₃, R^(C)S(O)—, R^(C)S(O)₂—, (R^(C))₂C═N—, R^(C)C(O)O—, R^(C)OC(O)—, R^(C)C(O)N(R^(N))—, (R^(C))₂NC(O)—, halogen, or —H, where R^(C), R^(N), and R^(P) are as defined above.

The catalyst system comprising a metal-ligand complex of formula (I) may be rendered catalytically active by any technique known in the art for activating metal-based catalysts of olefin polymerization reactions. For example, a metal-ligand complex of formula (I) may be rendered catalytically active by contacting the complex to, or combining the complex with, an activating co-catalyst. Suitable activating co-catalysts for use herein include alkyl aluminums; polymeric or oligomeric alumoxanes (also known as aluminoxanes); neutral Lewis acids; and non-polymeric, non-coordinating, ion-forming compounds (including the use of such compounds under oxidizing conditions). A suitable activating technique is bulk electrolysis. Combinations of one or more of the foregoing activating co-catalysts and techniques are also contemplated. The term “alkyl aluminum” means a monoalkyl aluminum dihydride or monoalkylaluminum dihalide, a dialkyl aluminum hydride or dialkyl aluminum halide, or a trialkylaluminum. Examples of polymeric or oligomeric alumoxanes include methylalumoxane, triisobutylaluminum-modified methylalumoxane, and isobutylalumoxane.

Lewis acid activators (co-catalysts) include Group 13 metal compounds containing from 1 to 3 (C₁-C20)hydrocarbyl substituents as described herein. Examples of Group 13 metal compounds are tri((C₁-C₂₀)hydrocarbyl)-substituted-aluminum or tri((C₁-C₂₀)hydrocarbyl)-boron compounds; tri(hydrocarbyl)-substituted-aluminum, tri((C₁-C₂₀)hydrocarbyl)-boron compounds; tri((C₁-C₁₀)alkyl)aluminum, tri((C₆-C₁₈)aryl)boron compounds; and halogenated (including perhalogenated) derivatives thereof. In further examples, Group 13 metal compounds are tris(fluoro-substituted phenyl)boranes, tris(pentafluorophenyl)borane. An activating co-catalyst can be a tris((C₁-C₂₀)hydrocarbyl borate (e.g. trityl tetrafluoroborate) or a tri((C₁-C₂₀)hydrocarbyl)ammonium tetra((C₁-C₂₀)hydrocarbyl)borane (e.g. bis(octadecyl)methylammonium tetrakis(pentafluorophenyl)borane). As used herein, the term “ammonium” means a nitrogen cation that is a ((C₁-C₂₀)hydrocarbyl)₄N⁺, a ((C₁-C₂₀)hydrocarbyl)₃N(H)⁺, a ((C₁-C₂₀)hydrocarbyl)₂N(H)₂ ⁺, (C₁-C₂₀)hydrocarbylN(H)₃ ⁺, or N(H)₄ ⁺, wherein each (C₁-C₂₀)hydrocarbyl, when two or more are present, may be the same or different.

Combinations of neutral Lewis acid activators (co-catalysts) include mixtures comprising a combination of a tri((C₁-C₄)alkyl)aluminum and a halogenated tri((C₆-C₁₈)aryl)boron compound, especially a tris(pentafluorophenyl)borane; or combinations of such neutral Lewis acid mixtures with a polymeric or oligomeric alumoxane, and combinations of a single neutral Lewis acid, especially tris(pentafluorophenyl)borane with a polymeric or oligomeric alumoxane. Ratios of numbers of moles of (metal-ligand complex): (tris(pentafluoro-phenylborane): (alumoxane) [e.g., (Group 4 metal-ligand complex) :(tris(pentafluoro-phenylborane):(alumoxane)] are from 1:1:1 to 1:10:30, or from 1:1:1.5 to 1:5:10.

The catalyst system comprising the metal-ligand complex of formula (I) can be activated to form an active catalyst composition by combination with one or more co-catalysts, for example, a cation forming co-catalyst, a strong Lewis acid, or combinations thereof. Suitable activating co-catalysts include polymeric or oligomeric aluminoxanes, especially methyl aluminoxane, as well as inert, compatible, noncoordinating, ion forming compounds. Exemplary suitable co-catalysts include, but are not limited to: modified methyl aluminoxane (MMAO), bis(hydrogenated tallow alkyl)methyl, tetrakis(pentafluorophenyl)borate(1⁻) amine, and combinations thereof.

One or more of the foregoing activating co-catalysts can be used in combination with each other. One preferred combination is a mixture of a tri((C₁-C₄)hydrocarbyl)aluminum, tri((C₁-C₄)hydrocarbyl)borane, or an ammonium borate with an oligomeric or polymeric alumoxane compound. The ratio of total number of moles of one or more metal-ligand complexes of formula (I) to total number of moles of one or more of the activating co-catalysts is from 1:10,000 to 100:1. The ratio can be at least 1:5000, or, at least 1:1000; and can be no more than 10:1 or no more than 1:1. When an alumoxane alone is used as the activating co-catalyst, preferably the number of moles of the alumoxane that are employed can be at least 100 times the number of moles of the metal-ligand complex of formula (I). When tris(pentafluorophenyl)borane alone is used as the activating co-catalyst, the ratio of the number of moles of the tris(pentafluorophenyl)borane that are employed to the total number of moles of one or more metal-ligand complexes of formula (I) can be from 0.5:1 to 10:1, from 1:1 to 6:1, or from 1:1 to 5:1. The remaining activating co-catalysts are generally employed in approximately mole quantities equal to the total mole quantities of one or more metal-ligand complexes of formula (I).

Nonwovens

A nonwoven formed from the bicomponent fiber described above is disclosed herein.

A nonwoven formed from the bicomponent fiber disclosed herein can be formed via different techniques. Such techniques for forming a nonwoven from a bicomponent fiber disclosed herein include melt spinning, melt blown process, spunbond process, staple process, carded web process, air laid process, thermo-calendering process, adhesive bonding process, hot air bonding process, needle punch process, hydroentangling process, and electrospinning process. For example, in one embodiment, a spunbond nonwoven comprising the bicomponent fiber according to embodiments disclosed herein can be formed. In other embodiments, a meltblown nonwoven comprising the bicomponent fiber according to embodiments disclosed herein can be formed.

A nonwoven formed from the bicomponent fiber disclosed herein can have a combination of lower denier, enhanced tensile strength, enhanced abrasion resistance, and/or higher elongation at break. In one or more embodiments herein, the nonwoven can exhibit one or more of the following properties: a fiber denier equal to or less than 1.5 g/9000 m (alternatively, equal to or less than 1.4 g/9000 m, equal to or less than 1.3 g/9000 m, or equal to or less than 1.2 g/9000 m, or in the range of from 0.8 to 2 g/9000 m, 1.0 to 1.8 g/9000 m, 1.0 to 1.6 g/9000 m, or 1.0 to 1.4 g/9000 m), where fiber denier is measured in accordance with the test method described below; a tensile strength in the machine direction (MD) of greater than 11.0 Newton per one inch (N/1 inch) (alternatively, greater than 13.0 N/1 inch, greater than 15.0 N/1 inch, or greater than 17.0 N/1 inch, or in the range of from 12.0 to 25 N/1 inch, 13.0 to 25 N/1 inch, 15.0 N/1 inch to 25 N/1 inch, or 18.0 N/1 inch to 25 N/1 inch) at 20 grams/square meter (gsm) of the nonwoven, where tensile strength is measured in accordance with the test method described below; an abrasion resistance in the machine direction (MD) of less than 0.18 mg/cm² (alternatively, less than 0.16 mg/cm², less than 0.14 mg/cm², less than 0.12 mg/cm², less than 0.10 mg/cm², less than 0.08 mg/cm², less than 0.06 mg/cm², or in the range of from 0.01 mg/cm² to 0.16 mg/cm², 0.01 mg/cm² to 0.12 mg/cm², or 0.01 mg/cm² to 0.06 mg/cm²) at 20 gsm of the nonwoven, where abrasion resistance is measured in accordance with the test method described below; and a percent (%) elongation at break in the machine direction (MD) of greater than 100% (alternatively, greater than 120%, greater than 140%, greater than 160%, or in the range of from 110% to 200%, 120% to 200%, 140% to 200%, or 160% to 200%) at 20 gsm of the nonwoven, where % elongation at break is measured in accordance with test method described below.

For example, the nonwoven according to embodiments disclosed herein can have a tensile strength in the machine direction (MD) of greater than 11.0 N/1 inch at 20 gsm of the nonwoven and a percent (%) elongation at break in the machine direction (MD) of greater than 100% at 20 gsm of the nonwoven. As another example, the nonwoven according to embodiments disclosed herein can have a tensile strength in the machine direction (MD) of greater than 11.0 N/1 inch at 20 gsm of the nonwoven and an abrasion resistance in the machine direction (MD) of less than 0.18 mg/cm² at 20 gsm of the nonwoven. As yet another example, the nonwoven according to embodiments disclosed herein can have a tensile strength in the machine direction (MD) of greater than 11.0 N/1 inch at 20 gsm of the nonwoven; a percent (%) elongation at break in the machine direction (MD) of greater than 100% at 20 gsm of the nonwoven; and an abrasion resistance in the machine direction (MD) of less than 0.18 mg/cm² at 20 gsm of the nonwoven.

A nonwoven formed from the bicomponent fiber disclosed herein can comprise at least 12 wt. % of the combined first ethylene/alpha-olefin interpolymer and second ethylene/alpha-olefin interpolymer at a temperature range of from 40.0° C. to 68.0° C. (WT_(40-68° C.)) on an elution profile via improved comonomer composition distribution (ICCD) procedure, where weight percent at a temperature range of from 40.0° C. to 68.0° C. on an elution profile via ICCD can be measured in accordance with the test method described below. All individual values and subranges of at least 12 wt. % are disclosed and included herein. For example, the nonwoven can comprise at least 12 wt. %, at least 14 wt. %, at least 18 wt. %, at least 22 wt. %, at least 26 wt. %, or at least 28 wt. % of the combined first ethylene/alpha-olefin interpolymer and second ethylene/alpha-olefin interpolymer at a temperature range of from 40.0° C. to 68.0° C. (WT_(40-68° C.)) on an elution profile via improved comonomer composition distribution (ICCD) procedure, where weight percent at a temperature range of from 40.0° C. to 68.0° C. on an elution profile via ICCD can be measured in accordance with the test method described below.

A nonwoven formed from the bicomponent fiber disclosed herein can comprise at least 6 wt. % of the combined first ethylene/alpha-olefin interpolymer and second ethylene/alpha-olefin interpolymer at a temperature range of from 40.0° C. to 65.0° C. (WT_(40-68° C.)) on an elution profile via improved comonomer composition distribution (ICCD) procedure, where weight percent at a temperature range of from 40.0° C. to 65.0° C. on an elution profile via ICCD can be measured in accordance with the test method described below. All individual values and subranges of at least 6 wt. % are disclosed and included herein. For example, the nonwoven can comprise at least 6 wt. %, at least 8 wt. %, at least 12 wt. %, at least 16 wt. %, at least 20 wt. %, or at least 22 wt. % of the combined first ethylene/alpha-olefin interpolymer and second ethylene/alpha-olefin interpolymer at a temperature range of from 40.0° C. to 65.0° C. (WT_(40-68° C.)) on an elution profile via improved comonomer composition distribution (ICCD) procedure, where weight percent at a temperature range of from 40.0° C. to 65.0° C. on an elution profile via ICCD can be measured in accordance with the test method described below.

A nonwoven formed from the bicomponent fiber disclosed herein can comprise at least 2 wt. % of the combined first ethylene/alpha-olefin interpolymer and second ethylene/alpha-olefin interpolymer at a temperature range of from 40.0° C. to 60.0° C. (WT_(40-68° C.)) on an elution profile via improved comonomer composition distribution (ICCD) procedure, where weight percent at a temperature range of from 40.0° C. to 60.0° C. on an elution profile via ICCD can be measured in accordance with the test method described below. All individual values and subranges of at least 2 wt. % are disclosed and included herein. For example, the nonwoven can comprise at least 2 wt. %, at least 4 wt. %, at least 6 wt. %, at least 8 wt. %, at least 10 wt. %, or at least 11 wt. % of the combined first ethylene/alpha-olefin interpolymer and second ethylene/alpha-olefin interpolymer at a temperature range of from 40.0° C. to 60.0° C. (WT_(40-68° C.)) on an elution profile via improved comonomer composition distribution (ICCD) procedure, where weight percent at a temperature range of from 40.0° C. to 60.0° C. on an elution profile via ICCD can be measured in accordance with the test method described below.

Test Methods Density

Density is measured in accordance with ASTM D-792, and expressed in grams/cm³ (g/cm³).

Melt Index (I2)

Melt Index (I2) is measured in accordance with ASTM D 1238 at 190° Celsius and 2.16 kg, and is expressed in grams eluted/10 minutes (g/10 min).

Conventional Gel Permeation Chromatography (Conventional GPC)

The chromatographic system consists of a PolymerChar GPC-IR (Valencia, Spain) high temperature GPC chromatograph equipped with an internal IR5 infra-red detector (IR5). The autosampler oven compartment is set at 160° C. and the column compartment is set at 150° C. The columns used are 4 Agilent “Mixed A” 30 cm 20-micron linear mixed-bed columns The chromatographic solvent used is 1,2,4 trichlorobenzene and contains 200 ppm of butylated hydroxytoluene (BHT). The solvent source is nitrogen sparged. The injection volume used is 200 microliters and the flow rate is 1.0 milliliter/minute.

Calibration of the GPC column set is performed with at least 20 narrow molecular weight distribution polystyrene standards with molecular weights ranging from 580 to 8,400,000 g/mol and are arranged in 6 “cocktail” mixtures with at least a decade of separation between individual molecular weights. The standards are purchased from Agilent Technologies. The polystyrene standards are prepared at 0.025 grams in 50 milliliters of solvent for molecular weights equal to or greater than 1,000,000 g/mol, and 0.05 grams in 50 milliliters of solvent for molecular weights less than 1,000,000 g/mol. The polystyrene standards are dissolved at 80° C. with gentle agitation for 30 minutes. The polystyrene standard peak molecular weights are converted to ethylene/alpha-olefin interpolymer molecular weights using the following equation (as described in Williams and Ward, J. Polym. Sci., Polym. Let., 6, 621(1968)):

M _(polyethylene) =A×(M _(polystyrene))^(B)   (Eq. 1)

where M is the molecular weight, A has a value of 0.4315 and B is equal to 1.0.

A fifth order polynomial is used to fit the respective ethylene/alpha-olefin interpolymer-equivalent calibration points. A small adjustment to A (from approximately 0.39 to 0.44) is made to correct for column resolution and band-broadening effects such that NIST standard NBS 1475 is obtained at a molecular weight of 52,000 g/mol.

The total plate count of the GPC column set is performed with Eicosane (prepared at 0.04 g in 50 milliliters of TCB and dissolved for 20 minutes with gentle agitation). The plate count (Equation 2) and symmetry (Equation 3) are measured on a 200 microliter injection according to the following equations:

$\begin{matrix} {{{Plate}{Count}} = {5.54 \times \left( \frac{RV_{{Peak}{Max}}}{{Peak}{Width}{at}{half}{height}} \right)^{2}}} & \left( {{Eq}.2} \right) \end{matrix}$

where RV is the retention volume in milliliters, the peak width is in milliliters, the Peak Max is the maximum height of the peak, and half height is one half of the height of the peak maximum.

$\begin{matrix} {{Symmetry} = \frac{\left( {{{Rear}{Peak}{RV}_{{one}{tenth}{height}}} - {RV}_{{Peak}\max}} \right)}{\left( {{RV}_{{Peak}\max} - {{Front}{Peak}{RV}_{{one}{tenth}{height}}}} \right)}} & \left( {{Eq}.3} \right) \end{matrix}$

where RV is the retention volume in milliliters and the peak width is in milliliters, Peak max is the maximum position of the peak, one tenth height is one tenth of the height of the peak maximum, and where rear peak refers to the peak tail at later retention volumes than the Peak max and where front peak refers to the peak front at earlier retention volumes than the Peak max. The plate count for the chromatographic system should be greater than 22,000 and symmetry should be between 0.98 and 1.22.

Samples are prepared in a semi-automatic manner with the PolymerChar “Instrument Control” Software, wherein the samples are weight-targeted at 2 mg/ml, and the solvent (contained 200 ppm BHT) is added to a pre nitrogen-sparged septa-capped vial, via the PolymerChar high temperature autosampler. The samples are dissolved for 3 hours at 160° C. under “low speed” shaking.

The calculations of M_(n(GPC)), M_(w(GPC)), and M_(z(GPC)) are based on GPC results using the internal IR5 detector (measurement channel) of the PolymerChar GPC-IR chromatograph according to Equations 5a-c, using PolymerChar GPCOne™ software, the baseline-subtracted IR chromatogram at each equally-spaced data collection point i (IR_(i)) and the ethylene/alpha-olefin interpolymer equivalent molecular weight obtained from the narrow standard calibration curve for the point i (M_(polyethylene,i) in g/mol) from Equation 1. Subsequently, a GPC molecular weight distribution (GPC-MWD) plot (wt_(GPC)(lgMW) vs. lgMW plot, where wt_(GPC)(lgMW) is the weight fraction of the interpolymer molecules with a molecular weight of 1gMW) can be obtained. Molecular weight is in g/mol and wt_(GPC)(lgMW) follows the Equation 4.

∫wt _(GPC)(lg MW)d lg MW=1.00   (Eq. 4)

Number-average molecular weight M_(n(GPC)), weight-average molecular weight M_(w(GPC)) and z-average molecular weight M_(z(GPC)) can be calculated as the following equations.

$\begin{matrix} {{Mn}_{({GPC})} = \frac{\sum\limits^{i}{IR}_{i}}{\sum\limits^{i}\left( {{IR}_{i}/M_{{polyethylene},_{i}}} \right)}} & \left( {{{Eq}.5}a} \right) \end{matrix}$ $\begin{matrix} {{Mw}_{({GPC})} = \frac{\sum\limits^{i}\left( {{IR}_{i}*M_{{polyethylene},_{i}}^{2}} \right)}{\overset{i}{\sum{IR}_{i}}}} & \left( {{{Eq}.5}b} \right) \end{matrix}$ $\begin{matrix} {{Mz}_{({GPC})} = \frac{\sum\limits^{i}\left( {{IR}_{i}*M_{{polyethylene},_{i}}^{2}} \right)}{\sum\limits^{i}\left( {{IR}_{i}*M_{{polyethylene},_{i}}} \right)}} & \left( {{{Eq}.5}c} \right) \end{matrix}$

In order to monitor the deviations over time, a flow rate marker (decane) is introduced into each sample via a micropump controlled with the PolymerChar GPC-IR system. This flow rate marker (FM) is used to linearly correct the pump flow rate (Flowrate(nominal)) for each sample by RV alignment of the respective decane peak within the sample (RV(FM Sample)) to that of the decane peak within the narrow standards calibration (RV(FM Calibrated)). Any changes in the time of the decane marker peak are then assumed to be related to a linear-shift in flow rate (Flowrate(effective)) for the entire run. To facilitate the highest accuracy of a RV measurement of the flow marker peak, a least-squares fitting routine is used to fit the peak of the flow marker concentration chromatogram to a quadratic equation. The first derivative of the quadratic equation is then used to solve for the true peak position. After calibrating the system based on a flow marker peak, the effective flow rate (with respect to the narrow standards calibration) is calculated as Equation 6. Processing of the flow marker peak is done via the PolymerChar GPCOne™ Software. Acceptable flow rate correction is such that the effective flowrate should be within 0.5% of the nominal flowrate.

Flow rate_(effective)=Flow rate_(nominal)×(RV(FM_(calibrated))/RV(FM_(Sample)))   (Eq. 6)

Improved Comonomer Composition Distribution (ICCD)

The Improved Comonomer Composition Distribution (ICCD) test is performed with Crystallization Elution Fractionation instrumentation (CEF) (PolymerChar, Spain) equipped with IR-5 detector (PolymerChar, Spain) and two-angle light scattering detector Model 2040 (Precision Detectors, currently Agilent Technologies). The ICCD column is packed with gold coated nickel particles (Bright 7GNM8-NiS, Nippon Chemical Industrial Co.) in a 15 cm (length)×¼″ (ID) stainless tubing. The column packing and conditioning are with a slurry method according to the reference (Cong, R.; Parrott, A.; Hollis, C.; Cheatham, M. WO2017040127A1, which is incorporated herein by reference). The final pressure with trichlorobenzene (TCB) slurry packing is 150 bars. The column is installed just before IR-5 detector in the detector oven. Ortho-dichlorobenzene (ODCB, 99% anhydrous grade or technical grade) is used as eluent. Silica gel 40 (particle size 0.2˜0.5 mm, catalogue number 10181-3) is obtained from EMD Chemicals and can be used to dry ODCB solvent. The ICCD instrument is equipped with an autosampler with nitrogen (N₂) purging capability. ODCB is sparged with dried N₂ for one hour before use. Sample preparation is done with autosampler at 4 mg/ml (unless otherwise specified) under shaking at 160° C. for 1 hour. The injection volume is 300 μl. The temperature profile of ICCD is: crystallization at 3° C./min from 105° C. to 30° C., then thermal equilibrium at 30° C. for 2 minutes (including Soluble Fraction Elution Time being set as 2 minutes), followed by heating at 3° C./min from 30° C. to 140° C. The flow rate during elution is 0.50 ml/min Data are collected at one data point/second. Column temperature calibration can be performed by using a mixture of the reference material linear homopolymer polyethylene (having zero comonomer content, melt index (I₂) of 1.0 g/10 min, polydispersity M_(w(GPC))/M_(n(GPC)) approximately 2.6 by conventional gel permeation chromatography, 1.0 mg/ml) and Eicosane (2 mg/ml) in ODCB. ICCD temperature calibration consists of four steps: (1) Calculating the delay volume defined as the temperature offset between the measured peak elution temperature of Eicosane minus 30.00° C.; (2) Subtracting the temperature offset of the elution temperature from the ICCD raw temperature data (it is noted that this temperature offset is a function of experimental conditions, such as elution temperature, elution flow rate, etc.); (3) Creating a linear calibration line transforming the elution temperature across a range of 30.00° C. and 140.00° C. so that the linear homopolymer polyethylene reference has a peak temperature at 101.0° C., and Eicosane has a peak temperature of 30.0° C.; and (4) For the soluble fraction measured isothermally at 30° C., the elution temperature below 30.0° C. is extrapolated linearly by using the elution heating rate of 3° C./min according to the reference (Cerk and Cong et al., U.S. Pat. No. 9,688,795, which is incorporated herein by reference).

Determination of Weight Percent on the ICCD Elution Profile

A single baseline is subtracted from the IR measurement signal in order to create a relative mass-elution profile plot starting and ending at zero relative mass at its lowest and highest elution temperatures (typically between 35° C. and 119° C.). For convenience, this is presented as a normalized quantity with respect to an overall area equivalent to 1. In the relative mass-elution profile plot from ICCD, a weight fraction (w_(T)(T)) (which can be converted into a weight percent) at each temperature (T) can be obtained. The profile (w_(T)(T) vs. T) id from 35.0° C. to 119.0° C. with a temperature step increase of 0.200° C. from the ICCD, and follows:

∫_(35.0) ^(119.0) w _(T)(T)dT=1   (Eq. 7)

The weight fraction (WT_(lower T−higher T)) can be calculated according to the following equation by integrating the w_(T)(T) vs. T profile over the temperature range of interest:

WT _(lower T−higher T)=∫_(lower T) ^(higher T) w _(T)(T)dT   (Eq. 8)

Tensile Strength and % Elongation at Break Test Methods

For tensile testing, 20 grams/square meter (gsm) nonwovens are cut into 1 inch by 8 inch rectangular strips in the machine direction (MD) for tensile testing using an Instron tensile tester. The strips are tested at a test speed of 300 mm/min with an initial grip-to-grip distance (L₀) of 76.2 mm. Nonwoven tensile strength of Newton/1 inch (N/1 inch width) is determined at the peak force. At the peak load, grip-to-grip distance (L) is read and percent (%) elongation at break is reported as (L−L₀)/L₀×100%. Average value of 5 samples is reported.

Abrasion Resistance Test Method

Abrasion resistance of the example nonwovens can be measured using a Sutherland Ink Rub Tester. Prior to testing, samples of 20 gsm nonwoven are cut into 12.5 cm×5 cm rectangular strips and are conditioned for a minimum of four hours at 73° F. +/−2 and constant relative humidity. A 12.5 cm×5 cm rectangular strip of 320-grit aluminum oxide cloth sandpaper is then mounted on the Sutherland Ink Rub Tester. The sample is then weighed to the nearest 0.01 mg and mounted onto the Tester. A 2 pound weight is then attached to the Sutherland Ink Rub Tester and the tester is run at a rate of 42 cycles per minute, for 20 cycles. Loose fibers are removed using adhesive tape, and the sample is re-weighed to determine the amount of material lost. Abrasion resistance is defined as the material loss in weight divided by the size of the abraded area. Units of abrasion resistance are mg/cm². Average value of 5 samples is reported.

Fiber Denier Measurement

Fiber diameter is measured via optical microscopy. Denier (defined as the weight of such fiber for 9000 meter) is calculated based on the density of each polymer component and fiber diameter.

Filament Speed Determination

Filament speed is calculated based on the following equation:

Filament Speed (meter per minute)=throughput rate (g/min)/denier(g/9000 m)*9,000   (Eq. 9)

Differential Scanning Calorimetry (DSC)

Differential scanning Calorimetry is used to measure the highest peak melting temperature (Tm) and the highest peak crystallization temperature (Tc) according to ASTM D3895-14. Approximately 0.5 gram of sample is compression molded into a film at 25,000 psi and 190° Celsius for 10-15 seconds. A 5 to 8 mg sample is weighed and placed in a DSC aluminum pan with the lid crimped on the pan to ensure a closed atmosphere. During testing, a nitrogen purge gas flow of 50 ml/min is used.

The thermal behavior of the sample is determined by ramping the sample temperature up and down to create a heat flow versus temperature profile. For cooling and second heat information, the sample is heated at a rate of 10° Celsius/minute to 150° Celsius and held isothermally for 5 minutes. The sample is then cooled at a rate of 10° Celsius/minute to −40° Celsius, held isothermally for 5 minutes before being heated at a rate of 10° Celsius/minute to 150° Celsius.

The cooling and second heating curves are recorded. The cool curve is analyzed by setting baseline endpoints from the beginning of crystallization to −20° C. The heat curve is analyzed by setting baseline endpoints from −20° C. to the end of melt. The values determined are highest peak melting temperature (Tm) and highest peak crystallization temperature (Tc). The highest peak melting temperature (Tm) is reported from the second heat curve. The highest peak crystallization temperature (Tc) is determined from the cooling curve.

EXAMPLES Production of Ethylene/Alpha-Olefin Interpolymers of Examples

Polymer 1 (Poly. 1), Polymer 2 (Poly. 2), and Polymer 3 (Poly. 3), which are ethylene/alpha-olefin interpolymers, are prepared according to the following process and tables.

All raw materials (monomer and comonomer) and the process solvent (a narrow boiling range high-purity isoparaffinic solvent, Isopar-E) are purified with molecular sieves before introduction into the reaction environment. Hydrogen is supplied pressurized as a high purity grade and is not further purified. The reactor monomer feed stream is pressurized via a mechanical compressor to above reaction pressure. The solvent and comonomer (if present) feed is pressurized via a pump to above reaction pressure. The individual catalyst components are manually batch diluted with purified solvent and pressured to above reaction pressure. All reaction feed flows are measured with mass flow meters and independently controlled with computer automated valve control systems.

Reactor configuration is either single reactor operation or dual series reactor operation as specified in Table 2A and 2B below.

Either a single reactor system or a two reactor system in a series configuration is used. Each reactor is a continuous solution polymerization reactor consisting of a liquid full, non-adiabatic, isothermal, circulating, loop reactor which mimics a continuously stirred tank reactor (CSTR) with heat removal. Independent control of all fresh solvent, monomer, comonomer (if present), hydrogen, and catalyst component feeds is possible. The total fresh feed stream to each reactor (solvent, monomer, comonomer [if present], and hydrogen) is temperature controlled typically between 15-50° C. to maintain a single solution phase by passing the feed stream through a heat exchanger. The total fresh feed to each polymerization reactor is injected into the reactor at two locations with approximately equal reactor volumes between each injection location. The fresh feed is controlled with each injector receiving half of the total fresh feed mass flow. The catalyst components are injected into the polymerization reactor through injection nozzles to introduce the components into the center of the reactor flow. The primary catalyst component feed is computer controlled to maintain the reactor monomer conversion at the specified values. The cocatalyst component(s) is/are fed based on calculated specified molar ratios to the primary catalyst component. Immediately following each reactor feed injection location, the feed streams are mixed with the circulating polymerization reactor contents with static mixing elements. The contents of each reactor are continuously circulated through heat exchangers responsible for removing much of the heat of reaction and with the temperature of the coolant side responsible for maintaining an isothermal reaction environment at the specified temperature. Circulation around each reactor loop is provided by a pump.

In dual series reactor configuration the effluent from the first polymerization reactor (containing solvent, monomer, comonomer [if present], hydrogen, catalyst components, and polymer) exits the first reactor loop and is added to the second reactor loop. In all reactor configurations the final reactor effluent (second reactor effluent for dual series or the single reactor effluent) enters a zone where it is deactivated with the addition of and reaction with a suitable reagent (water). At this same reactor exit location other additives are added for polymer stabilization (e.g., antioxidants suitable for stabilization during extrusion and fabrication include Octadecyl 3,5-Di-Tert-Butyl-4-Hydroxyhydrocinnamate, Tetrakis(Methylene(3,5-Di-Tert-Butyl-4-Hydroxyhydrocinnamate))Methane, and Tris(2,4-Di-Tert-Butyl-Phenyl) Phosphite).

Following catalyst deactivation and additive addition, the reactor effluent enters a devolatization system where the polymer is removed from the non-polymer stream. The isolated polymer melt is pelletized and collected. The non-polymer stream passes through various pieces of equipment which separate most of the ethylene which is removed from the system. Most of the solvent and unreacted comonomer (if present) is recycled back to the reactor after passing through a purification system. A small amount of solvent and comonomer (if present) is purged from the process.

The reactor stream feed data flows that correspond to the values in Tables 2A and 2B used to produce the polymers are graphically described in FIG. 1 and FIG. 2 . The data are presented such that the complexity of the solvent recycle system is accounted for and the reaction system can be treated more simply as a once through flow diagram.

TABLE 1 Catalyst Components Primary Catalyst Component 1

Primary Catalyst Component 2

Primary Catalyst Component 3

Co-catalyst A bis(hydrogenated tallow alkyl)methylammonium tetrakis(pentafluorophenyl)borate(1-) Co-catalyst B Modified methyl aluminoxane Co-catalyst C Triethyl aluminum

TABLE 2A Production Configurations for Poly. 3 Poly. 3 Reactor Configuration Type Single Comonomer type Type 1-hexene Reactor Feed Solvent/ g/g 3.47 Ethylene Mass Flow Ratio Reactor Feed Comonomer/ g/g 0.009 Ethylene Mass Flow Ratio Reactor Feed Hydrogen/ g/g 3.10E−04 Ethylene Mass Flow Ratio Reactor Temperature ° C. 185 Reactor Pressure barg 38 Reactor Ethylene % 93.6 Conversion Reactor Catalyst Type Type Primary Catalyst (See also Table 1) Component 1 Reactor Co-Catalyst 1 Type Type Co-catalyst A (See also Table 1) Reactor Co-Catalyst 2 Type Type Co-catalyst C (See also Table 1) Reactor Co-Catalyst 1 to mol/mol 1.1 Catalyst Molar Ratio (B to Catalyst Metal ratio) Reactor Co-Catalyst 2 to mol/mol 2 Catalyst Molar Ratio (Al to Catalyst Metal ratio) Reactor Residence Time min 12.6

TABLE 2B Production Configurations for Poly. 1 and Poly. 2 Poly. 1 Poly. 2 Reactor Configuration Type Dual Series Dual Series Comonomer type Type 1-octene 1-octene First Reactor Feed Solvent/ g/g 3.13 3.34 Ethylene Mass Flow Ratio First Reactor Feed Comonomer/ g/g 0.331 0.111 Ethylene Mass Flow Ratio First Reactor Feed Hydrogen/ g/g 3.35E−04 2.34E−04 Ethylene Mass Flow Ratio First Reactor Temperature ° C. 160 160 First Reactor Pressure barg 40 50 First Reactor Ethylene % 89.7 94.6 Conversion First Reactor Catalyst Type Type Primary Catalyst Primary Catalyst (See also Table 1) Component 2 Component 2 First Reactor Co-Catalyst 1 Type Type Co-catalyst A Co-catalyst A (See also Table 1) First Reactor Co-Catalyst 2 Type Type Co-catalyst B Co-catalyst B (See also Table 1) First Reactor Co-Catalyst 1 to mol/mol 1.2 1.1 Catalyst Molar Ratio (B to Catalyst Metal ratio) First Reactor Co-Catalyst 2 to mol/mol 39 20 Catalyst Molar Ratio (Al to Catalyst Metal ratio) First Reactor Residence Time min 17.8 17.9 Percentage of Total Ethylene wt % 37.9% 37.2% Feed to First Reactor Second Reactor Feed Solvent/ g/g 2.45 2.53 Ethylene Mass Flow Ratio Second Reactor Feed g/g 0.134 0.044 Comonomer/Ethylene Mass Flow Ratio Second Reactor Feed Hydrogen/ g/g 6.27E−04 4.66E−04 Ethylene Mass Flow Ratio Second Reactor Temperature ° C. 195 195 Second Reactor Pressure barg 40 50 Second Reactor Ethylene % 91.6 91.9 Conversion Second Reactor Catalyst Type Type Primary Catalyst Primary Catalyst (See also Table 1) component 3 component 3 Second Reactor Co-Catalyst 1 Type Co-catalyst A Co-catalyst A Type (See also Table 1) Second Reactor Co-Catalyst 2 Type Co-catalyst B Co-catalyst B Type (See also Table 1) Second Reactor Co-Catalyst 1 to mol/mol 5.5 7.6 Catalyst Molar Ratio (B to Catalyst Metal ratio) Second Reactor Co-Catalyst 2 to mol/mol 2249 1387 Catalyst Molar Ratio (Al to Catalyst Metal ratio) Second Reactor Residence Time min 7.5 7.4

The following ethylene/alpha-olefin interpolymers are also used in the examples.

Polymer 4 (Poly. 4) is ASPUN™ 6850A, an ethylene/alpha-olefin interpolymer commercially available from The Dow Chemical Company (Midland, Mich.).

Polymer 5 (Poly. 5) is ASPUN™ 6835A, an ethylene/alpha-olefin interpolymer commercially available from The Dow Chemical Company (Midland, Mich.).

Polymer 6 (Poly. 6) is ASPUN™ 6000, an ethylene/alpha-olefin interpolymer commercially available from The Dow Chemical Company (Midland, Mich.).

Polymer 7 (Poly. 7) is DOWLEX™ 2517, an ethylene/alpha-olefin interpolymer commercially available from The Dow Chemical Company (Midland, Mich.).

Polymer 8 (Poly. 8) is ELITE 5860, an ethylene/alpha-olefin interpolymer commercially available from The Dow Chemical Company (Midland, Mich.).

Table 3 below provides the Melt Index (I2), Density, M_(w(GPC))/M_(n(GPC)), highest peak crystallization temperature (Tc), and highest peak melting temperature (Tm) of Poly. 1 to Poly 8.

TABLE 3 Characteristics of Poly. 1 to Poly. 8 Highest Melt Highest Peak Index Density Mw_((GPC))/ Crystallization Melting (g/10 min) (g/cm³) Mn_((GPC)) Temp. (Tc) Temp. (Tm) Poly. 1 19 0.935 2.1 113° C. 127° C. Poly 2. 19 0.945 2.4 115° C. 128° C. Poly 3. 19 0.949 2.2 114° C. 128° C. Poly. 4 30 0.955 3.1 116° C. 130° C. Poly. 5 17 0.950 3.3 114° C. 129° C. Poly. 6 19 0.935 2.7 112° C. 127° C. Poly. 7 25 0.917 3.6 102° C. 123° C. Poly. 8 21.5 0.907 2.6  96° C. 123° C.

Formation of Fibers and Nonwovens

Spunbond nonwovens are formed from bicomponent fibers and produced on a single beam Reicofil 4 spunbond line in a 50:50 (in weight percent) concentric core:sheath configuration. The core of the bicomponent fiber is an ethylene/alpha olefin interpolymer composition as reported in Table 4. The sheath is the same or a different ethylene/alpha olefin interpolymer composition as reported in Table 4. The machine (Reicofil 4 spunbond line) is equipped with a spinneret having 7022 holes (6861 holes/m) and an exit diameter of each hole of 0.6 mm. The hole has a L/D ratio of 4. The polymer melt temperature is set at approximately 230° C. Fibers are collected at the maximum sustainable cabin air pressure while maintaining stable fiber spinning and transformed into a nonwoven of target basis weight 20 gsm. Bonding of the web takes place between an engraved roll and a smooth roll with a nip pressure of 70 daN/cm. The oil temperature of the engraved roll is adjusted for achieving the best bonding without overwrapping the nonwoven onto the roll. The oil temperature of the smooth roll is kept at 2° C. lower than that of the engraved roll.

The example nonwovens formed from the bicomponent fibers have been designated as Inventive and Comparative Examples as reported in Table 4. The fiber denier of the nonwovens, as well as the difference in highest peak melting temperature (ΔTm), difference in highest peak crystallization temperature (ΔTc), and difference in density (ΔDensity) between the first region minus the second region of the bicomponent fibers are reported in Table 5.

Weight percent (wt. %) of the combined first ethylene/alpha-olefin interpolymer and second ethylene/alpha-olefin interpolymer at temperature ranges of from 40.0° C. to 68.0° C. (WT_(40-68° C.)), 40.0° C. to 65.0° C. (WT_(40-65° C.)), and 40.0° C. to 60.0° C. (WT_(40-60° C.)) on the ICCD elution profile of the nonwoven examples is reported in Table 6. Referring now generally to FIG. 3 , an ICCD elution profile of nonwoven Inventive Example 2 is shown. The combined weight percent of Poly. 3 and Poly. 8 of Inventive Example 2 is equal to 30% (as reported in Table 6) at a temperature range of from 40.0° C. to 68.0° C. (WT_(40-68° C.)) on the ICCD elution profile. The inventive nonwovens, Inventive Example 1 and Inventive Example 2, have higher weight percent of the two polymers of the regions on the ICCD elution profile, which, without being bound by theory, contributes to the enhanced properties of abrasion resistance, tensile strength, and/or percent elongation at break.

Additional processing conditions for the nonwoven are reported in Table 7. Additional properties of the nonwoven are shown in Table 8. The inventive nonwovens, Inventive Example 1 and Inventive Example 2, have a fine fiber denier while having a higher ΔTm, ΔTc, and ADensity, which, without being bound by theory, contributes to enhanced properties of abrasion resistance, tensile strength, and/or percent elongation at break in comparison to the comparative nonwovens, Comparative Examples 1-8.

TABLE 4 Composition of Bicomponent Fibers for Forming Nonwovens Fiber First Fiber Second Weight Ratio - Region Region First Region to Nonwoven Example (Core) (Sheath) Second Region Inventive Ex. 1 Poly. 3 Poly. 7 50:50 Inventive Ex. 2 Poly. 3 Poly. 8 50:50 Comparative Ex. 1 Poly. 6 Poly. 6 50:50 Comparative Ex. 2 Poly. 1 Poly. 1 50:50 Comparative Ex. 3 Poly. 4 Poly. 4 50:50 Comparative Ex. 4 Poly. 2 Poly. 2 50:50 Comparative Ex. 5 Poly. 5 Poly. 6 50:50 Comparative Ex. 6 Poly. 4 Poly. 1 50:50 Comparative Ex. 7 Poly. 2 Poly. 1 50:50 Comparative Ex. 8 Poly. 3 Poly. 1 50:50

TABLE 5 Denier, ΔDensity, ΔTc, and ΔTm data Nonwoven Fiber First Region Fiber Second Region Fiber Denier Example (Core) (Sheath) (g/9000 m) ΔTc ΔTm ΔDensity Inv. Ex. 1 Poly. 3 Poly. 7 1.1 12° C.  5° C. 0.032 g/cm³ Inv. Ex. 2 Poly. 3 Poly. 8 1.4 18° C.  5° C. 0.042 g/cm³ Comp. Ex. 1 Poly. 6 Poly. 6 1.8 0° C. 0° C. 0 g/cm³ Comp. Ex. 2 Poly. 1 Poly. 1 1.5 0° C. 0° C. 0 g/cm³ Comp. Ex. 3 Poly. 4 Poly. 4 1.6 0° C. 0° C. 0 g/cm³ Comp. Ex. 4 Poly. 2 Poly. 2 1.5 0° C. 0° C. 0 g/cm³ Comp. Ex. 5 Poly. 5 Poly. 6 1.7 2° C. 2° C. 0.015 g/cm³ Comp. Ex. 6 Poly. 4 Poly. 1 1.6 3° C. 3° C. 0.020 g/cm³ Comp. Ex. 7 Poly. 2 Poly. 1 1.6 2° C. 1° C. 0.010 g/cm³ Comp. Ex. 8 Poly. 3 Poly. 1 1.1 1° C. 1° C. 0.014 g/cm³

TABLE 6 ICCD Data of Nonwoven Examples Nonwoven ICCD ICCD ICCD Example WT_(40-68° C.) WT_(40-65° C.) WT_(40-60° C.) Inv. Ex. 1 13%  10%   5% Inv. Ex. 2 30%  23%   12% Comp. Ex. 1 5% 3%  1% Comp. Ex. 2 11%  5%  1% Comp. Ex. 3 0.9%  0.7%  0.5% Comp. Ex. 4 0.5%  0.3%  0.2% Comp. Ex. 5 5% 3% 0.8% Comp. Ex. 6 6% 2% 0.3% Comp. Ex. 7 5% 2% 0.4% Comp. Ex. 8 3% 1% 0.3%

TABLE 7 Additional Conditions for Forming Nonwovens Optimized Throughput Filament Cabin Engraved Rate Nonwoven Speed Pressure Roll (gram/hole/ Example (m/min) (Pa) Temp. minute) Inv. Ex. 1 4582 5400 112° C. 0.56 Inv. Ex. 2 3600 4300 102° C. 0.56 Comp. Ex. 1 2800 2300 124° C. 0.56 Comp. Ex. 2 3360 4000 124° C. 0.56 Comp. Ex. 3 3150 3000 124° C. 0.56 Comp. Ex. 4 3360 3300 124° C. 0.56 Comp. Ex. 5 2965 2300 122° C. 0.56 Comp. Ex. 6 3150 3000 124° C. 0.56 Comp. Ex. 7 3150 4000 124° C. 0.56 Comp. Ex. 8 4582 5400 124° C. 0.56

TABLE 8 Properties of Nonwoven: Tensile Strength in the Machine Direction (MD) at 20 gsm reported in Newton per one inch (N/1 inch); Abrasion Resistance in the MD at 20 gsm reported in mg/cm²; and % Elongation at break in the MD at 20 gsm. Tensile Abrasion % Elongation Strength in MD Resistance in at Break Nonwoven (N/1 inch @ MD (mg/cm² @ in MD @ Example 20 gsm) 20 gsm) 20 gsm Inv. Ex. 1 13.6 0.10 120% Inv. Ex. 2 18.0 0.05 163% Comp. Ex. 1 9.3 0.20  76% Comp. Ex. 2 8.7 0.35  50% Comp. Ex. 3 9.7 0.46  28% Comp. Ex. 4 10.4 0.56  72% Comp. Ex. 5 11.0 0.12 133% Comp. Ex. 6 9.9 0.05 128% Comp. Ex. 7 10.6 0.11 102% Comp. Ex. 8 16.2 0.21  81%

Every document cited herein, if any, including any cross-referenced or related patent or application and any patent application or patent to which this application claims priority or benefit thereof, is hereby incorporated herein by reference in its entirety unless expressly excluded or otherwise limited. The citation of any document is not an admission that it is prior art with respect to any invention disclosed or claimed herein or that it alone, or in any combination with any other reference or references, teaches, suggests or discloses any such invention. Further, to the extent that any meaning or definition of a term in this document conflicts with any meaning or definition of the same term in a document incorporated by reference, the meaning or definition assigned to that term in this document shall govern.

While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention. 

1. A bicomponent fiber comprising: a first region and a second region; the first region comprising a first ethylene/alpha-olefin interpolymer having a highest peak melting temperature (Tm) of less than 130° C. when measured by DSC; the second region comprising a second ethylene/alpha-olefin interpolymer having a density less than a density of the first ethylene/alpha-olefin interpolymer composition; wherein the highest peak melting temperature (Tm) of the first ethylene/alpha-olefin interpolymer is at least 3.5° C. greater than a highest peak melting temperature (Tm) of the second ethylene/alpha-olefin interpolymer, where highest peak melting temperature (Tm) is measured by DSC; wherein the first region and second region are arranged in a core-sheath configuration.
 2. The bicomponent fiber of claim 1, wherein the first ethylene/alpha-olefin interpolymer has a highest peak crystallization temperature (Tc) at least 3.5° C. greater than a highest peak crystallization temperature (Tc) of the second ethylene/alpha-olefin interpolymer, where highest peak crystallization temperature (Tc) is measured by DSC.
 3. The bicomponent fiber of claim 1, wherein the density of the first ethylene/alpha-olefin interpolymer is at least 0.022 g/cm³ greater than the density of the second ethylene/alpha-olefin interpolymer.
 4. A nonwoven formed from the bicomponent fiber of claim 1, wherein the nonwoven has one or more of the following properties: a fiber denier equal to or less than 1.5 g/9000 m; a tensile strength in the machine direction greater than 11.0 Newton per one inch at 20 gsm of the nonwoven; an elongation at break in the machine direction greater than 100% at 20 gsm of the nonwoven; and an abrasion resistance in the machine direction of less than 0.18 mg/cm² at 20 gsm of the nonwoven.
 5. A nonwoven formed from the bicomponent fiber of claim 1, wherein the nonwoven comprises at least 12 wt. % of the combined first ethylene/alpha-olefin interpolymer and second ethylene/alpha-olefin interpolymer at a temperature range of from 40.0° C. to 68.0° C. (WT_(40-68° C.)) on an elution profile via improved comonomer composition distribution (ICCD) procedure.
 6. A nonwoven formed from the bicomponent fiber of claim 1, wherein the nonwoven has a fiber denier equal to or less than 1.5 g/9000 m; a tensile strength in the machine direction greater than 11.0 Newton per one inch at 20 gsm of the nonwoven; an elongation at break in the machine direction greater than 100% at 20 gsm of the nonwoven; and an abrasion resistance in the machine direction of less than 0.18 mg/cm² at 20 gsm of the nonwoven. 